Known washing machines comprise a drum that is rotated by means of a main motor in accordance with a speed order corresponding to the various phases of a washing program selected by a user, and a drainage pump with a discharge motor to drain the flow of water that has accumulated in the drum. The main motor is usually of the universal motor type, with the speed being regulated by phase control and tachometer feedback. The main motor is controlled by a control device that acts on a switch, normally a triac. The time reference that is normally used to carry out the phase control of the main motor is the zero setting of the mains voltage.
The control device also controls the discharge motor of the drainage pump, using a respective switch, normally a triac, to do so. The discharge motor is usually a synchronous permanent-magnet motor and is usually operated, through the triac, by an on-off control.
GB 2274343 describes a control device for a washing machine that controls the discharge motor of the drainage pump. The control device uses an on-off control to operate the discharge motor, in other words, the discharge motor is powered in the phases in which an amount of water has to be drained from the drum, with the discharge motor not being powered in the phases in which there is no water.